Sealed insulator bushing



" and tube 5.

Patented Nov. 11, 1952 `UNITED STATES PATENT OFFICE SEALED INSULATORBUSHING Hugh Carmichael, Deep River, Ontario, Canada Application April5, 1949, Serial No. 85,600 In Canada June 17, 1948 6 Claims. 1

'making such insulators because this material has substantially perfectinsulating properties and is comparatively very slowly deteriorated bylneutron or other radiation. However, considerable pressures, of theorder of 1000 pounds 'per square inch, must be imposed on the quartzpartsof the insulator in order to obtain gas f tight joints, andordinary quartz parts do not possess sucient inherent strength towithstand such heavy loads. It is an object of this invention to providean insulator having quartz insulating members therein so constructed asto possess sufficient inherent mechanical strength to withstand loads ofthe'order of at least 1000 pounds per square inch.

The invention will be described with reference to the accompanyingdrawing, in which Figure 1 is a longitudinal section through aninsulator in accordance with the invention,

Figure 2 is a plan view of a quartz insulating member, and

Figure 3 is an elevation of a fragmentary portion of the quartzinsulating member.

In the drawing, I is a substantially cylindrical 4insulator housingmounted in a wall 2 of an ionisation chamber or the like.

- quartz rings 1 of similar size and shape, fitting over the extendingend portions of the bolt 3 One ring is inserted between the head 8 ofthe bolt and the adjacent end of the bushing, and the other ring isinserted between the other end of the bushing and a washer 0. A nut I0is screwed onto the outer end of bolt 3 to secure the parts in assembledrelation. Soft metal, preferably lead or gold, gaskets H are `insertedbetween the opposing surfaces of the rings l with the washer 9, bushing4, and bolt e.:

head 8. The metal surfaces of the latter members in contact with thegaskets are preferablyl provided with a plurality of concentric V-shapedgrooves l2. by means of the nut I0, the grooves l2 divide the gasket llinto a plurality of substantially Vindependent ring seals i3 whicheffectively render the insulator vacuum and pressure tight.

It will be observed that the tube 5 terminatesV in slightly spacedrelation to washer 9 and head 8 and thus is not subjected to pressurestresses;

In order to obtain the necessary sealing contact between the parts, itis essential to screw up the bolt to a tension of the order of 1000' thetreatment of the rings to render them pressure resistant.

The rings are first washed in chromic acid toY remove traces of abrasiveand then in several changes of distilled water. An Oxy-hydrogen ame isthen directed onto the edges and surface of the ring to round the edgesto a radiusv of, for instance, s1; inch, as indicated at I4, and

to fire-polish the surface, thus producing a smooth glazed finishthereon. The, microscopic and larger cracks normally present in a quartzsurface are thus sealed up. During the firing operation, the surfaceportion of the quartz ring becomes melted, which, on solidiflcation,forms a dense coherent surface.

Following the initial fire-polishing step, the at surfaces of the ringsare finely ground or lapped to true up the same whereby such surfacesare plane and parallel to an accuracy of, say, 0.0001 inch. The finelyground surfaces are then regulated with an Oxy-hydrogen name, great carebeing taken not to impair their flatness appreciably.

It has been found that quartz rings having their edges rounded and theirflat surfaces firepolished and glazed are capable of withstanding loadsof 1000 lbs. per square inch and greater.

In order to prevent the setting up of strains on the quartz rings in theassembly by irregularities in the lead gaskets, it is advisable tosubject the assembled insulator to a heat treatment at a temperaturenear the melting point of lead whereby the lead nows into intimatecontact with the quartz and metal and irregularities are elim-` inated.Such heat treatment when carried out in vacuo also serves to free thequartz from any Thus on compression of the parts'- absorbed moisture andtherefore increases the insulation resistance thereof.

It is desirable to employ, in the assembly, a bolt of such length,diameter, and elasticity that, when loaded to apply a pressure of about1000 lbs. per square inch on the insulating members, it is elongation asa result of the load is sufiicient to be at least about 25% in excess ofthe original combined thickness of the gaskets Il. In other words, thesum of the thickness of the two gaskets is less than the amount ofelongation of the bolt. This ensures that the gaskets always remaintight.

I claim:

1. An insulating member comprising a bolt having a head, a bushing and awasher o n the bolt, a quartz ring interposed between the head of thebolt and the bushing and between the washer and the bushing, and a nuton the bolt compressing said washer, bushing, and quartz rings under apressure of at least 1000 lbs. per square inch, each. said quartz ringhaving flat, parallel,v opposite surfaces receiving said compressiveforce, each said surface having that degree vof smoothness, denseness4and mergence with contiguous surfaces which is attainable `by firepolishing.

2. In a gas tight insulating joint, a quartz insulating member having atparallelopposite surfaces, and metallic clamping means engaging said.surfaces to make gas-tight joints therewith, said surfaces having thatdegree of smoothness, .denseness and mergence with contiguous surfacesvof the member which is attainable by fire polishing, whereby saidvinsulating member is adapted to. withstand clamping pressures ofthe-order of 1000 lbs. per square inch.

.3. In a gas tight insulating joint, ,a quartz insulating ring havingfiat parallel opposite annular surfaces and co-axial cylindricalsurfaces, and metallic clamping means engaging said annular surfaces tomake gas-tight joints therewith, said clamping means including a rodpassing axially through said ring, said annular surfaces havingthatdegree of smoothness, densenessand mergence with said cylindricalsurfaces which is attainable by re polishing, whereby saidinsulatingring is `adapted to withstand clamping pressures of the order of 1000lbs. per square inch.k

4. A gas tight insulating joint, comprising a quartz body having aresistance to fracture and a high degree of external smoothness of theorder obtained by re polishing, at least one member having a surface incontact with the surface of said body over a substantial area, and meansfor pressing said body and said member together under a pressure up to1000 lbs. per square inch.

5. A joint as set forth in claim 4, in which said quartz body hasopposing parallel surfaces, and said members are two in number and arein contact one with each of said parallel surfaces.

6. A method of preparing a smooth, quartz insulating element having atleast two parallel surfaces and havinga resistance to pressure of theorder of 1000 lbs. per square inch, comprising the steps of washing abody of quartz having at least two substantially parallel surfaces in astrong'acid, washing said body in distilled water, subjecting said bodyto intense fire-polishing heat, grinding saidsurfaces to an accuracy of.0001 inch in atness and parallelism, and. iirepolishing said groundsurfaces, whereby the surfaces of said body are rendered extremelysmoothand the resistance of the body to fracture isfgreatly increased.-

Y HUGH CARMICHAEL.

vRBFIGREN CES CITED The following references are of record inlthe illeof this patent:

UNITED STATES 'PATENTS OTHER REFERENCES Thomson: GeneralElectric Review,Feb.- 1923, vol. XXVI, No. 2, pages 68 through '74.v

